Okay, there are a few things I have contemplated with my engine.

First, it has 202K miles on it, has needed a valve cover gasket for at
least the past 22K miles (since I purchased the car), and hasn't had
regular oil changes with the exception of the last two which were done
on time.

The engine gets really bad gas mileage, and it is a 2.3L, 4 cylinder
engine.  Acceleration is poor at best.  I highly doubt this has
anything to do with the transmission, as the fluid still appears to be
brand new and tranny only has 82K miles on it.

My main question is what is typically the approximate cost of having
either a new or rebuilt engine installed as a general estimate?

Many people question why I would spend the money for a new engine on an
older car.  First, I have put this car through so much, and it has
treated me right the whole time, I don't want to get rid of it because
I know I can trust it. Second, if I have to spend the money on either a
car I know the quirks of, or a different used car which may have its
own problems that need ironing out, I would rather put the money into a
car that I know.

Thanks in advance for any ideas on price range,
Toby Barnett